A class-action lawsuit filed yesterday in a U.S. District Court in California alleges that the biggest names in online travel — Priceline, Expedia, Travelocity, Orbitz, Hotels.com — and some of the world’s largest hotel chains — Hilton, Starwood, Marriott, Intercontinental, among others — conspired together so that the “best price guarantee” you often see when booking a room online is in actuality just a number set by the hotel operators.